On Wed, 9 Jul 2008 09:51:05 EDT, Davy
wrote:

I have several oxygenators in my limestone pebble lined
pond. Unfortunately, many of them become covered in
limescale; at best they look unattractive: at worst they
die.

Can anybody suggest plants that are likely to thrive?

String algae lives well in mine!

Actually I think most ponders depend on waterfalls, air pumps or
sprays that send a flow of water into the air for oxygen. Especially
since plants at night consume oxygen and give off carbon dioxide.
--
Hal Middle Georgia, Zone 8
http://tinyurl.com/2fxzcb